I don't have much advice but I'm interested in what others will say.
My experience...I'm also an English Lit major but ended up going a much more corporate route into editing. My first job after school was a temp job for a publishing firm, but I didn't love that industry. During school, off and on I worked for an academic research firm, editing and content web/SEO writing, working with grad students and professors on dissertations, theses, manuscripts, and journal article submissions. I used that as a jumping off point to medical editing, working for consultants on research, clinical trials, advertising to Drs, promotions, and branding. Clients are huge pharma companies such as Janssen (Johnson & Johnson), Takeda, Genentech, Novartis, Bayer, Bristol-Myers Squibb, and Eisai. It's proven to be very lucrative and there are many flexible work-from-home opportunities out there. Idk whether you'd be interested in any of the above that I mentioned. Bad news: you'd likely have to start entry level and work up from there. Good news: you don't need any further education whatsoever.
Would you mind going into more detail about your library work? I considered it at one point but didn't want to back to school for the MLS. What do you do every day? How much do you make? I don't think I'd want to change things up right now as I'm being paid easily the most I have in my whole life for an easy (to me) job. However, it's always nice to know what's out there and have options in the back pocket. You mention boredom as a negative...Idk if I'm not driven or very lazy, but I always viewed boredom as a positive in a job! I work about half of the time I'm in the office and I've become an expert at time-wasting (MMM forums as one avenue) for the other half.
Finally, the narrative that there are no jobs for English majors is simply false. I've listed three separate industries I worked in above, and I'm not even 30. Now, if you want to be well compensated, you'll have to go the corporate route and stay away from the creative and "fun" fields.
I haven't even mentioned the big freelancing industry for editing and writing. That's something I want to try in the future, but haven't done so yet. The way I see it, there's no point in getting more busy now to make more $ until I've mastered spending habits and Mustachianism at my current income level.